1. Field of the Invention
The present invention generally relates to marine transmissions and, more particularly, to a type of marine transmission that uses electrorheological or magnetorheological fluids.
2. Background of the Invention
Many different types of marine transmissions are known to those skilled in the art. In addition, various types of electrorheological and magnetorheological materials have been used in devices that benefit from variable viscosity fluids. Magnetorheological and electrorheological fluids have been used in conjunction with clutches, mounts which provide a controlled variable stiffness, and other components which benefit from the use of fluids that can change viscosity in an advantageous way.
U.S. Pat. No. 4,444,298, which issued to Stangroom on Apr. 24, 1984, describes a viscous shear clutch. An electrorheological fluid is used as a transmission fluid between confronting, rotatable sets of clutch plates across which a potential difference can be applied so as to vary the viscous shear characteristic of the interjacent fluid. Differential arrangements of the clutch plates ensure cancellation of residual drag effects and the clutch can be electrically varied substantially from complete disengagement to solid engagement.
U.S. Pat. No. 4,664,236, which issued to Stangroom on May 12, 1987, describes an electrically controlled progressive, frictional, torque transmitting device. It comprises a rotary element, a proportion of the rotary power available from the rotary element, being used, under the control of a direct electrical signal, to determine the degree of engagement of a frictional device, and hence the torque transmitted or absorbed by the torque transmitting device, thereby avoiding the requirement for an additional power source to activate the frictional device whole.
U.S. Pat. No. 5,094,328, which issued to Palmer on Mar. 10, 1992, describes an electrorheological clutch apply system. Two sets of interleaved plates are disposed within a stationary housing. The first set of plates is fixed to the stationary housing. The second set of plates is fixed to a shaft rotatable relative to the housing. A piston is coaxially disposed against the plates at one end of the interleaved plates. A piston apply chamber is located in the stationary housing on the opposite side of the piston. The electrorheological fluid is circulated through the system by a pump, passing by the apply side of the piston, then between the plates, and then back to the pump. When there is a voltage potential between the plates, the flow between the plates is restricted and the pressure of the fluid on the piston builds, displacing the piston toward the plates. The plates are moved closer together by the piston. Contact between the plates is prevented by insulating elements mounted to alternate surfaces of the plates.
U.S. Pat. No. 5,779,013, which issued to Bansbach on Jul. 14, 1998, describes a torque transfer apparatus using magnetorheological fluids. The torque transfer device modulates the amount of torque which is transmitted from an input shaft to an output shaft. The torque transfer device includes a first plate connected to the input shaft. A second plate is connected to the output shaft and spaced from the first plate. A magnetorheological fluid is provided between the first and second plates.
U.S. Pat. No. 5,915,513, which issued to Isley et al. on Jun. 29, 1999, describes a clutch with magnetorheological operator for transfer cases and the like. A multiple disc clutch pack includes a pilot magnetorheological operator which controls operation of an associated ball ramp operator which, in turn, compresses a clutch pack to selectively transfer torque between the input member and an output member.
U.S. Pat. No. 5,988,336, which issued to Wendt et al. on Nov. 23, 1999, describes a clutch with electrorheological or magnetorheological liquid pushed through an electrode or magnetic gap by means of a surface acting as a piston. The device relates to a controllable clutch based on electrorheological or magnetorheological liquids, in which the transmission of force or the transmission of torque is achieved in that an electrorheological or magnetorheological liquid is pushed through an electrode gap or magnet gap of the clutch by means of a surface acting as a piston.
U.S. Pat. No. 6,062,360, which issued to Shields on May 16, 2000, discloses a synchronizer for a gear shift mechanism for a marine propulsion system. A synchronized gear shift mechanism is provided for a marine propulsion system. Using a hub and a sleeve that are axially movable relative to an output shaft but rotationally fixed to the shaft and to each other, the gear shift mechanism uses associated friction surfaces to bring the output shaft up to a speed that is in synchronism with the selected forward or reverse gear prior to mating associated gear tooth surfaces together to transfer torque from an input shaft to an output shaft.
U.S. Pat. No. 6,102,827, which issued to Teasdale et al. on Aug. 15, 2000, describes a clutch assembly with a planetary gear set. A clutch includes a stationary housing member, a rotating member supported for rotation with respect to the stationary housing member, and a planetary gear assembly operably interconnecting the rotating member to an output shaft. An actuating mechanism includes a magnetorheological fluid and a plurality of actuation coils. An electric current is supplied to create a magnetic flux. When a current is applied to the coils, the rotating member is placed in the engaged position and when there is no current in the coils, the rotating member is in the disengaged position.
U.S. Pat. No. 6,241,067, which issued to Wick on Jun. 5, 2001, describes a mechanical clutch. It has two elements which, for the purpose of positively engaging one another, are provided with opposed end toothings which are adapted to one another, the first element being rotatably mounted and axially supported, the second element also being rotatably mounted and axially supported, and further being axially blocked in a first position for the purpose of being non-rotatably engaged with the first element, and being axially movable into a position in which it is freely rotatably and disengaged from the first element, with a device for selectively axially blocking the second element. The clutch comprises a cavity system whose shape is variable and which is filled with a magnetorheological fluid.
U.S. Pat. No. 6,544,083, which issued to Sawyer et al. on Apr. 8, 2003, discloses a shift mechanism for a marine propulsion system. The mechanism is provided in which a cam structure comprises a protrusion that is shaped to extend into a channel formed in a cam follower structure. The cam follower structure can be provided with first and second channels that allow the protrusion of the cam to be extended into either which accommodates both port and starboard shifting mechanism.
U.S. Pat. No. 6,635,189, which issued to Suh et al. on Oct. 21, 2003, describes an electrorheological fluid comprising dried water soluble starch as a conductive particle. The electrorheological fluid comprising water soluble starch as conductive particles contains less than 5% water, by weight. The ER fluid comprises water soluble starch as a conductive particle which is dispersed in non-conductive media. It exhibits considerable electrorheological effect even though the amount of water contained in the fluid is reduced. Thus, it can be widely applicable to water sensitive damping devices and power devices such as a suspension system, a vibration damper or an engine mount, a brake, a clutch, and so forth. It is feasible for various fields such as an automatic and an aerospace industry.
U.S. Pat. No. 6,817,961, which issued to Moore et al. on Nov. 16, 2004, describes a magnetically responsive limited slip differential. It includes a case, a pair of pinion gears, a pair of side gears and an electrically operable coupling including a magnetically responsive fluid. The coupling selectively drivingly interconnects one of the side gears and the case. In one instance, it includes a rotor having a plurality of outwardly extending blades positioned in communication with a magnetorheological fluid.
U.S. Pat. No. 6,960,107, which issued to Schaub et al. on Nov. 1, 2005, discloses a marine transmission with a cone clutch used for direct transfer of torque. When in a forward gear position, torque is transmitted from an input shaft, or driving shaft, to an output shaft, or driven shaft, solely through the cone clutch. When in forward gear position, driving torque between the driving and driven shafts is not transmitted through any gear teeth. When in reverse gear position, torque is transmitted through an assembly of bevel gears.
U.S. Pat. No. 6,966,805, which issued to Caldwell on Nov. 22, 2005, discloses a marine transmission with synchronized engagement of a dog clutch. A marine transmission for connecting a driven shaft to a driving shaft is provided with first and second dog clutch members and first and second friction clutch members which are actuated, respectively, by first and second hydraulically actuated devices. Engagement of the friction clutch members with each other creates rotation of the driven shaft that approaches or equals the rotational speed of the driving shaft so that subsequent engagement of the first and second dog clutch members can be accomplished without significant relative rotational speed differences between the two dog clutch members.
U.S. Pat. No. 7,214,111, which issued to Phillips et al. on May 8, 2007, discloses a position sensor for a gear shift assist mechanism in a marine propulsion device. The shift mechanism is provided with a position identification device that incorporates one or more probes in association with one or more depressions that identify alignment between various positions on the piston and cylinder of the shift assist mechanism.
U.S. Pat. No. 7,291,048, which issued to Phillips et al. on Nov. 6, 2007, discloses an actuator device for a marine propulsion transmission. An actuator of a marine propulsion transmission is attached to a movable clutch member through the use of a coupler which comprises a generally spherical member formed as a portion of the actuator and a chuck device formed as part of the clutch member.
U.S. Pat. No. 7,297,036, which issued to Weronke et al. on Nov. 20, 2007, discloses a marine retention system for a marine propulsion device. In a marine transmission, trailing faces of each of a plurality of gear projections extending axially from a forward gear are provided with a rake angle. This rake angle of each trailing face cooperates with an associated surface of each of a plurality of clutch projections to retain a dog clutch in an axial position relative to the forward gear even during periods when a marine vessel is rapidly decelerating and, as a result, the dog clutch moves into driving relation with the forward gear.
In a paper titled “Fundamental Study of Fluid Transfer Using Electrorheological Effect”, Tanaka and Gofuku describe a new type of pump that can feed electrorheological fluid by utilizing the change in physical properties of the fluid by the application of voltage.
In an article titled “Testing Viscosity of MR Fluid in Magnetic Field”, by Roszkowski, Bogdan, Skoczynski, and Marek, in volume 8, Section 3, No. 3, 2008 of MEASUREMENT SCIENCE REVIEW, the properties of magnetorheological fluids are discussed along with methods for determining the coefficient of viscosity of MR fluids for different values of magnetic field.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Marine transmissions can benefit from a system which allows a shifting of the transmission without having to engage a generally stationary component with a component which is rotating at a greater speed. When a propeller shaft is suddenly engaged in torque transmitting relation with a driveshaft of an engine, the instantaneous shock loads can be significant. This can cause noise and potentially reduce the life of components within the transmission. This shock load can be significantly exacerbated when a propeller, attached to the propeller shaft, exhibits significant inertia and is stationary when an associated dog clutch is engaged between the stationary propeller shaft and a rotating driveshaft. It would therefore be significantly beneficial if an efficient and compact transmission could provide a method for avoiding these shock loads during a shifting procedure between neutral and either forward or reverse gear positions.